What are the advantages and disadvantages of referencing business logic to interfaces in a system?

The link of business logic to interfaces in Go provides the following advantages:

• Flexibility and extensibility: business logic depends on abstractions rather than concrete implementations, making it easier to replace components.
• Testability: interfaces can be easily mocked for unit testing.
• Loose coupling: reduces dependencies between modules, improving maintainability and scalability.

Disadvantages:

• Complexity of understanding: beginners may find it harder to follow the logic due to abstractions.
• Code redundancy: sometimes it requires writing many interfaces and adapters, increasing the code volume.
• Overcomplication: using interfaces unnecessarily can lead to excessive architectural complexity.

Example:

// Interface for user repository
type UserRepository interface {
    GetUser(id int) (*User, error)
}

// Business logic depends on the interface, not on a specific implementation
func GetUserName(repo UserRepository, id int) (string, error) {
    user, err := repo.GetUser(id)
    if err != nil {
        return "", err
    }
    return user.Name, nil
}

Thus, it is easy to replace UserRepository for tests or change the implementation without modifying the business logic.